An electronic device such as a smart phone may have a coil antenna for magnetic field communication such as near field communication (NFC) or magnetic secure transmission (MST). In addition, the electronic device may further have a coil antenna for charging a battery.
Specifically, the electronic device may include a communication circuit and a coil antenna electrically connected thereto. The communication circuit may output an electric signal to the coil antenna, and the coil antenna may generate a magnetic field signal using the energy of the electric signal and then emit the magnetic field signal to the exterior. In order to increase the power transmission efficiency of the magnetic field signal, the coil antenna may be designed to have low impedance. In the receive path, the coil antenna may receive a magnetic field signal, generate an electric signal using the energy of the magnetic field signal, and output the electric signal to the communication circuit. To increase the power reception efficiency of the magnetic field signal, the coil antenna may be designed with a relatively high impedance.
As described above, when the coil antenna is designed to have low impedance, the reception performance of the electronic device may deteriorate. On the contrary, when the coil antenna is designed to have high impedance, the transmission performance may deteriorate.